Fluoride 2004;37(4):271–277 Research report 271
FLUORIDE AND MAGNESIUM CONTENT IN SUPERFICIAL ENAMEL LAYERS OF TEETH WITH EROSIONS Danuta Waszkiel,a Krystyna Opalko,b Ryta Łagocka,c Dariusz Chlubekd Bia³ystok and Szczecin, Poland
SUMMARY: In the absence of any previous research on the content of fluoride and magnesium in superficial enamel layers of eroded teeth in relation to acid resistance of the enamel, a study was undertaken to determine the concentration of both elements in eroded teeth using the acid biopsy technique. Biopsies were obtained from the labial surface below (upper dentition) or above (lower dentition) the erosion from the following teeth: one upper central incisor, five upper canines, three lower canines, two upper premolars, and three lower premolars. Corresponding teeth without erosions from age- and gender-matched patients living in the same area served as controls. Microsamples of enamel were obtained using 3 µL of 0.5 M perchloric acid. Fluoride concentrations were measured chromatographically, and magnesium and calcium were determined by atomic absorption spectrometry. Teeth with enamel erosions had significantly lower concentrations of both fluoride and magnesium as well as lower resistance to penetration by acid. Significantly lower concentrations of fluoride and magnesium were found in upper as well as in deeper enamel layers of eroded teeth compared to controls. These findings confirm an association between the content of fluoride and magnesium and acid resistance in dental enamel, which is reduced in teeth with erosions. In areas of low exposure to fluoride, topical fluoride may be protective against enamel erosion by acids, especially in carbonated beverages. Keywords: Enamel acid biopsy; Dental enamel erosion; Enamel fluoride; Enamel magnesium. INTRODUCTION
Enamel erosion results from the action of acids on hard dental tissues. Numerous predisposing factors interacting with individually varying structural features and chemical composition of enamel play an important role in the etiology of these lesions.1-4 Enamel is essentially composed of hydroxyapatite and an organic matrix fraction containing proteins, lipids, and water. Hydroxyapatite contains calcium ions replaceable by sodium, magnesium, zinc, strontium, or lead ions, as well as hydroxyl and phosphate groups which can be substituted by chloride, bicarbonate, and fluoride ions giving rise to apatites with reduced calcium content (carboxyapatites, chloroapatites, fluoroapatites, etc.).5-7 Enamel and other hard dental tissues are eroded by acids from food or produced by bacteria in the dental plaque. Since the resistance of enamel to acids depends largely on its chemical composition, it is of interest to determine the composition that supports or prevents the process of erosion. Accordingly, this work was undertaken to determine the content of fluoride and magnesium in the superficial layers of enamel of teeth with erosions using the acid biopsy technique. aDept.
of Pediatric Dentistry, Academy of Medicine, Bia³ystok, bDept. of Propedeutics of Dentistry, cDept. of Conservative Dentistry, and dDept. of Biochemistry and Chemistry, Pomeranian Medical University, Szczecin, Poland. For correspondence: D Chlubek, Dept. of Biochemistry and Chemistry, Pomeranian Medical University, al. Powstańców Wlkp. 72, 70111 Szczecin, Poland. E-mail:
[email protected] Fluoride 2004;37(4)
272 Waszkiel, Opalko, Łagocka, Chlubek MATERIALS AND METHODS
Fourteen teeth with enamel erosions were studied in six males and eight females, aged 18-30 years, living in the city of Białystok, a poorly industrialized north-eastern region of Poland. Corresponding teeth without erosions from age and gender-matched patients living in the same area served as controls. All examined individuals completed a questionnaire concerning nutritional preferences, oral hygiene, and tooth brushing habits. Patients with enamel erosions consumed citrus fruits, apples, fruit juices, carbonated drinks, and herbal teas more frequently than those without erosions. No significant differences in oral hygiene and tooth brushing practices were found between the two groups. Biopsies were obtained from the labial surface below (upper dentition) or above (lower dentition) the erosion from the following teeth: one upper central incisor, five upper canines, two upper premolars, three lower canines, and three lower premolars. Enamel samples were collected from recumbent patients. The dental surface was mechanically cleaned with a brush, thoroughly rinsed with distilled water, dried, and defatted with ether. Contamination with saliva was prevented and an adhesive tape with a central hole measuring 1.75 mm in diameter and 2.4 mm2 in area was placed over the tooth. Microsamples of enamel were obtained using 3 µL of 0.5 M perchloric acid (HClO4) and an Eppendorf micropipette (Varipette 4710) with a plastic disposable tip. The acid droplet was dispensed with the tip positioned vertically to the dental surface under the hole, left for 3 s, and aspirated. The biopsied surface was rinsed with distilled water, dried, and a second sample was collected in the same manner. Fast remineralization of the biopsy site was ensured with Duraphat sealant. The enamel biopsy was placed in 1.5 mL Safe-Lock tube (Eppendorf, Germany) which was then sealed and stored at 4 ºC. Tubes were transported in dry ice for determination of fluoride, calcium, and magnesium content at the laboratory of the Department of Biochemistry and Chemistry, Pomeranian Medical University in Szczecin. Fluoride concentrations were measured with a Chrom 5 gas chromatograph (Laboratorni Pristroje).8,9 For this purpose, 50 µL of a solution containing 10 µL trimethylchlorosilane (TMCS) and 0.1 µL 2-methylbutane in 20 mL of benzene was added to each tube. Tubes were shaken for 20 min to transform TMCS into trifluoromethylsilane, which passed from the aqueous solution into the benzene layer. Phases were separated by centrifugation for 1 min, and 2 µL of the benzene phase was injected into the chromatograph. Prior to determination of magnesium and calcium content with atomic absorption spectrometry,10 tubes were evaporated to dryness, and 2 mL of 0.1% lanthanum solution was added. Measurements were performed with a PU 9100X instrument (Philips) in acetylene-oxygen flame and 1% solution of La(NO3)3 at a wavelength of 285.2 nm for magnesium and 422.7 nm for calcium. The mass of enamel samples was calculated on the base of calcium measurements, taking 37.4% as the content of calcium.11 The thickness of each biopsied Fluoride 2004;37(4)
Fluoride and magnesium in enamel of eroded teeth 273
layer was estimated using 2.95 g/cm3 as the enamel density and assuming cylindrical digestion of the enamel by perchloric acid. The following equation was used:8 enamel mass d
x π r2
= 2.95
where d = depth of penetration (biopsied layer thickness); 2.95 = density of enamel (g/cm3); r = radius of digestion (0.0875 cm). The results were submitted to a statistical comparison with the Student’s t test (Statgraphic 5.0 software) and tested for a significance level of p< 0.05 or less. RESULTS AND DISCUSSION
Mean mass and thickness of the enamel layers are given in Table 1. In teeth with erosions, both the enamel mass and calculated depth of acid penetration (layer thickness) were significantly greater than in the control group (p
